Driving mechanism for sleeve valves



Feb. 24, 1942.

G. S. KAMMEQR DRIVING MECHANISM FOR SLEEVE VALVES Filed July 17, 194i 3 Sheets-Sheet 1 flaw; 7, M w

Feb. 24, 1942. G. s. KAMMER DRIVING MECHANISM FOR SLEEVE VALVES Filed July 17, 1941 s Sheets-Sheet 2 Feb. 24, 1942. s, RI

' DRIVING MECHANISM FOR SLEEVE VALVES Filed July 17, 1941 3 Sheets-Sheet 3 expensive finishing operations.

Patented Feb. 24, 1942 George" Stephen KammerfMid dleton, I Ilkley, England near Application my 17, 1941, Serial No. 402,887 In Great Britain July 16, 1940 7 Claims.

vstroke cycle engines and especially those having the scavenging arrangements disclosed in my copendin patent application Serial Number 405,-

096, filed August 1, 1941.

The main object; of the invention is to provide a cyclic variation in the movement of the sleeve, with a prolonged dwell around th'einer dead centre of the sleeve travel, that is to say when the sleeve is nearest to the cylinder head.

It is a further object of the invention to provide a cheap mechanism of this kind which will operate satisfactorily. l l

The applicant has already disclosed mechanisms for the purpose in View, but such mechanisms may sometimes be too bulky and heavy when applied to small engines. The present invention aims at providing a mechanism or light weight, small bulk and having few parts of such form as to require complicated jigs or Thus the present driving mechanism is adapted for mass production.

A further object of the invention is to obtain an asymmetrical variation in the movement of the sleeve in regard to its inward and outward strokes. Such a variation could be obtained with the earlier mechanisms referred to but at the expense of some complication .in construction. The mechanism according to the present invention is bound to produce a certain-asymmetry in the mQtion though such asymmetry may be made so small as to be practically negligible;

The advantage of the asymmetry is that the sleeve can be made to move faster on its outward travel than on its inward travel. Consequently the engine can be timed for a more rapid exhaust port opening and have admission ports of larger area than previously. The open area of the admission port integrated with respect to time is then substantially increased over that of an engine with symmetrical sleeve motion.

According to the invention the sleeve valve of a two-stroke internal combustion engine is driven through. a drag-link mechanism having unequal pins of the two cranks, so that both cranks execute the same number of revolutions-per minute,

but the instantaneous angular speeds of the cranks are different. If the driving. crank is rotated at a uniform angular speed, the driven crank will rotate at a higher angular speed at one part of its travel and at a lower angular speed at another part. It is not considered necessary here to enter into amathematical discussion of the mechanism, but it should be pointed out that with beyond certain limiting relative dimensions of crank, link and spacing of centres a mechanism can be obtained which will only oscillate the driven crank. Such a mechanism falls'outside the scope of the above definition and accordingly outside the scope of the present invention.

In the preferred construction according to the invention the sum of the length of the drag link and the throw of the driven crank exceeds the sum of the separation of the shaft centres and the throw of the driving crank by an exceedingly small amount, which may be of the order of .001" or .025 mm;, the driving crank then being the one with the larger throw.

The accompanying drawings serve to explain th princ'iple: of operation and show some embodiments of the invention, and therein- Figure -1 is a line diagram drawn to certain relative dimensions,

Figure 2 is an endview of one form of driving mechanism having the same relative dimensions,

Figure 3 is an elevation partly in section corresponding to Figure 2, r

Figure 4 is a diagram showing the resulting valve movement plotted against engine crank angle,

Figure 5 is a transverse section through a preferred embodiment of the invention,

Figure 6 is an axial section of the same, and

Figure 7 is aha-1f end elevation of the same.

Referring first to Figure 1, the driving crank is centred at X and has a length in arbitrary units'of 156. The driven crank is centered at O, the length OX being '72 and the crank length 84. The link length is 145, and it will be seen that the sum of driven crank and link is 229, while the sum of driving crank and centre distance is 228.

The pin of the driven crank l follows the smaller circle and that of the driving crank .2 the larger circle, and in this instance the two circles touch each other since 84+72=156. The circle marked 2 is divided into equal arcs of 22 and for each point the drag-link 3 is drawn in t to define the position of the pin of the crank 2 on the smaller circle. At the upper part of the circle these points are closely spaced, indieating a pronounced dwell of the driven crank here, while at the lower part of the circle the points are more widely spaced. The right-hand side of the circle shows a wider spacing of the points than the left, or, in other words, the valve moves more rapidly on its outward travel than on its inward travel.

Referring now to Figures 2 and 3, a rotary member I is mounted on an axis by means of roller bearings 4 in a housing 5 attached to the engine crank case. A rotary member 2 is mounted on an axis X by means of roller bear ings 6 in a housing I also attached to the engine crank case. Crank pins 8 and 9 extenld on opposite sides from the member I and in line with each other. The crank pin 9 is connected by a sliding ball and socket joint ID to the sleeve II.

The rotary member 2 is keyed to a driving shaft I2, which is positively driven from the engine crank shaft. A crank pin I3 on the member 2 is linked to the crank pin 8 on the member I by the drag-link 3 through roller bearings.

In Figure 4 the sleeve travel is plotted against the angular movement of the member 2 starting from the point marked I in Figure 1 as origin. The sleeve reaches its inner dead centre position at about 30 but is practically stationary from about 350 through 0 to 130. its outer dead centre position at 235. ton dead centres are at 88 and 268 points being marked C and A respectively.

With a sleeve travel of 28 and piston stroke of 110 units, the sleeve edge movement, represented by the curve I4, first uncovers the exhaust at the point Z at 193 The piston travel is represented by the curve I5. The upper edge of the admission ports in the sleeve is represented by the curve I6. Curves I5 and I6 intersect at the point W at 226, where the admission ports commence to open and to admit scavenge air.

The sleeve reaches its outer dead centre posi tion at B at 235, and the admission ports open rapidly, until at 270 they reach their maximum opening of 18 lengthunits. At 295 the exhaust ports close, and from then until 320 the charge of fresh air enters, after which compression starts. The phase displacement between the piston and valve at the outer dead centre is 33 To provide a different timing, which may be desirable in some cases, the dotted curve I! might be used for the upper edge of the admission ports in the sleeve.

The timing may also be varied by altering the phase difference or by changing the length of travel of the sleeve.

The arrangement shown in Figures 2- and 3 is set out as an example of a constructional form of the invention and has been chosen on account of its simplicity for the purpose of explanation. Such an arrangement would, however, require considerable space in the axial direction of the shafts. The preferred arrangement is shown in Figures 5, 6 and '7 and is drawn to the same relative dimensions as Figures 2 and 3.

One difference is that the crank 9 is diametrically opposite to the crank 8. The bottom position of the crank 8 thus corresponds to the inner dead centre of the sleeve. Partly on account of this inversion the whole mechanism has been compressed in the axial direction. The housings 5 and I are combined into one member I8 having an aperture I9, through which a gear wheel (not shown.) can mesh with teeth 20 cut on the The pisthe It reaches periphery of the member 2 between two roller races. The member 2 is recessed to accommodate the link 3 and'the crank pin 8 of the member I. Both crank pins 8 and 9 are hollowed for lightness as may be seen from an inspection of Figure 6, where the section is taken through the center lines of the crank pins.

With the arrangement now disclosed the overall dimensions of the driving gear can be made about 35% less than those of the driving gear according to my Patent No. 2,197,107, issued April 16, 1940, and the production costs can be reduced to one-sixth or one-seventh as compared with the earlier mechanism.

Various modifications may be made in the constructional forms actually shown and described without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. In an internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member driven on a fixed axis, a crank on the rotary member, a second rotary member with its axis fixed and parallel to but displaced from that of the first rotary member, a crank on the second rotary member having a throw diiferent from that of the crank on the first rotary member, a link joining the two cranks, and a driving connection between the second rotary member and the sleeve valve.

2. In a two-stroke internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member driven on a fixed axis at the same speed as the engine, a crank on the rotary member, a second rotary member with its axis fixed and parallel to but displaced from that of the first rotary member, a crank on the second rotary member having a throw smaller than that of the crank on the first rotary member, a link joining the two cranks, and a driving connection between the second rotary member and the sleeve valve.

3. In an internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member driven on a fixed axis, a crank on the rotary member, a second rotary member with its axis fixed and parallel to but different from that of the first rotary member, a crank on the second rotary member having a throw smaller than that of the crank on the first rotary member, a link joining the two cranks, and a driving connection between the second rotary member and the sleeve valve, in which the sum of the throw of the second crank and the length of the link only slightly exceeds the sum of the throw of the first crank and the distance between the axes of the rotary members.

4. In an internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member driven on a fixed axis, a crank on the rotary member, a second rotary member with its axis fixed and parallel to but displaced from that of the first rotary member, a crank on the second rotary member having a throw different from that of thecrank on the first rotary .member, a link joining the two cranks, another crank on the second rotary member, and a universal and sliding joint connection between the last-named crank and the sleeve valve.

5. In an internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member of disc shape in a fixed housing, a crank pin on the rotary member, a second rotary member of disc shape smaller than the first rotary member and rotatable in the same housing on an axis spaced from but parallel to that of the first member, a crank pin on the sec- 0nd member projecting into a recess in the first member, a link within the recess joining the two crank pins, and a driving connection between the second rotary member and the sleeve valve.

6. In a two-stroke internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of said sleeve valve comprising a rotary member of disc shape driven at the same speed as the engine in a fixed housing, a crank pin on the rotary member, a second rotary member of disc shape smaller than the, 2 first rotary member and rotatable in the same housing on an axis spaced from but parallel to that of the first member, a crank pin on the second member projecting into a recess in the first member, a link within the recess joining the two crank pins, a further crank'on the side .of the second rotary member away from the first rotary member, and a sliding and universal joint between the last-named crank and the sleeve valve.

7. In an internal combustion engine with a sleeve valve having an oscillating and reciprocating motion, means to provide a cyclic variation in the movement of the said sleeve valve comprising a fixed housing, a disc member rotatable in the housing, roller bearings between the disc member and the housing, a crankpin projecting from the disc member, a second disc member rotatable in the housing on an axis parallel to but spaced from the axis of rotation of the first disc member, roller bearings between the second disc member and. the housing, a crank pin projecting from the second disc member into a recess in the first, a link coupling the two crank pins, and roller bearings between each crank pin and the link.

GEORGE STEPHEN KAMMER. 

